1. Field of the Invention
The present invention relates to an amplifier circuit for amplifying a high-frequency signal and a receiving device, and particularly to a wide-band amplifier circuit of a negative feedback type and a receiving device including the amplifier circuit.
2. Description of the Related Art
Amplifier circuits in related art are known for amplifying a signal received via an antenna. Of the amplifier circuit in related arts, an amplifier circuit using a grounded-emitter circuit in a first stage and using an emitter follower in a succeeding stage will be described with reference to FIG. 11.
FIG. 11 is a diagram showing an open gain amplifier circuit 110 using a grounded-emitter circuit as a transistor in a first stage and using an emitter follower as a transistor in a succeeding stage.
The first stage transistor Q101 in the amplifier circuit 110 of FIG. 11 forms a grounded-emitter circuit that receives a high-frequency signal from a base (input terminal) and then outputs a first amplified signal from a collector. The first amplified signal output from the collector of the first stage transistor Q101 is input to the base of a succeeding stage transistor Q102. Then, an inverted signal amplified with a gain Av≈R102/R103 with respect to the input voltage can be obtained from the emitter of the succeeding stage transistor Q102.
In addition, an invention of a negative feedback amplifier having a capacitance added in parallel with a feedback resistance is known (see for example, Japanese Patent No. 2752795, hereinafter referred to as Patent Document 1).
The negative feedback amplifier shown in FIG. 1 of Patent Document 1 is an amplifier formed by a cascade connection of a collector-load grounded-emitter amplifier circuit in a preceding stage formed by connecting a collector resistance RC1, an NPN-type bipolar transistor Q1, and an emitter resistance RE1 in series with each other and an amplifier circuit in a succeeding stage formed by a collector resistance RC2, an NPN transistor Q2, and an emitter resistance RE2 between a high-level power supply terminal and a grounding terminal. In order to widen a frequency band, an emitter peaking capacitor C1 is connected in parallel with the emitter resistance RE2 in the succeeding stage. Further, negative feedback is effected by connecting a feedback resistance RF1 and a capacitance CF1 in parallel with each other between the emitter of the NPN transistor Q2 in the succeeding stage and the base of the NPN transistor Q1 in the preceding stage.